One known optical scanning apparatus is, for example, a scanning endoscope that vibrates an emission end of an optical fiber in two dimensions with an actuator, scans an object being observed (irradiated portion) spirally with illumination light passing from the optical fiber through an illumination optical system, and generates an image by detecting signal light, such as scattered light, from the object being observed. In such a scanning endoscope, the scanning position on the object being observed and the pixel position in the generated image need to be matched accurately.
As one method for doing so, patent literature 1 (PTL 1), for example, discloses a method to detect the scanning trajectory of the scanning endoscope with a position sensitive detector (PSD) and to calibrate the driving voltage applied to the actuator so that the scanning trajectory can become a predetermined standard scanning trajectory. In greater detail, the calibration method of PTL 1 sets the frequency of the driving voltage so as to maximize the amplitude of the scanning trajectory, sets a phase difference of the driving voltage in two dimensions so that the scanning trajectory can become a substantially true circle, and sets the maximum amplitude of the driving voltage in two dimensions so that the magnitude and shape of the scanning trajectory can be within predetermined ranges.